NITROGEN DYNAMICS AND NITRATE LEACHING UNDER PASTURELAND ECOSYSTEM

摘要

Water resources protection from nitrate-nitrogen (NO_3-N) contamination due to agricultural practices if, of important public concerns Surface water contamination with nitrate from grazed pasture agroecosystem, particularly those fertilized with slurry, has been a major environmental issue and possible health risk in many paris of the world. The main objectives of this study were to evaluate the nitrogen fertilizer management strategy and the nitrate leaching component of a pasture agroecosystem in Siggen, southeast Baden-Wurttemberg, Germany under slurry application for two consecutive years to asses its potential risk on grounc.water vulnerability to NO_3-N contamination. Three different rates of slurry were applied representing local practice (Intensive Fertilized Plot, IFP), reduced rate received 60% of the IFP (Reduced Fertilized Plot, RFP), and zero fertilization (Zero Fertilized Plot, ZFP). Results indicated that pasture dry matter yield and total soil N increased with slurry application. Itwas also evident that intensive slurry application builds up the soil organic matter (SCM) pool. Mineralization rate of SOM was slow due to the environmental conditions of the region. Soil moisture contents did not vary widely due to the humid condition, According to the calculated values cf water percolation and nitrate concentration measured in the soil-water samples at 80 cm depth, the amount of NO_3-N leached from the slurry treated plots were threefold of the untreated plots. In all plots, the amounts of water percelation were high and NO_3-N concentrations were low. Data from dry matter yield coupled with nitrate leaching suggested that ths RFP treatment represented the best management practices to the study area at Siggen.